Abstract [en]

To meet the demands from their customers Volvo Powertrain has set a new production goal for cylinder heads for 13-liter diesels engines. The production lines are built as a flow line of grouped CNC machines, served by a gantry for loading and unloading. The new production goal for one of the production lines, segment 2, is 33 cylinder heads per hour. Volvo Powertrain has also found through the production monitoring-system, Duga, that the waiting time for the loading equipment is a significant amount of the available production time.

The aim of this project is hence twofold: (1) to verify that the calculations of the waiting time made in Duga are correct; (2) to investigate and propose improvements for the production line in order to achieve the original targeted production goal. This has been done by using simulation and simulation-based optimization technology and for this purpose a generic simulation module of a gantry was made. This project will not answer questions regarding economic consequences, staffing and quality losses in the production line.

A simulation model has been built in the first phase of the project for a machining cell in Segment 2, which contains one gantry for the loading and unloading operations of four different CNC machining centers connected in series. The simulation model shows that the waiting time of the loading equipment in real time is not as big as what is calculated in Duga. This discrepancy is due to a misleading definition of the waiting time made in Duga.

The generic gantry module has been used to build a simulation model of Segment 2. Three different optimization runs has been made with an optimization client from the University of Skövde. One of the optimization runs found a solution that matches Volvo Powertrains production goal. From this optimization run one preferred and realistic solution was chosen. The solution includes new levels in buffers along the production line, line balancing and improved availability to the different machines and gantries. The preferred and realistic solution increases the production rate by 10%.